1. Technical Field
The invention relates in general to a package, and more particularly to a semiconductor package.
2. Description of the Related Art
As technologies developing, the size of on-chip structures shrinks and the frequency of on-chip circuit increases, leading to rapid growth in on-chip bandwidth. Similar improvements in the size and speed of off-chip structures are lacking, giving rise to a gap between on-chip and off-chip bandwidth and hence a performance bottleneck.
Proximity communication aims to solve the off-chip bandwidth bottleneck. Proximity communication is based on the observation that faster, lower-cost communication is possible over shorter distances. Placing the transmitter and receiver in extremely close proximity, with only microns of separation between them, should therefore lower overall communication costs. This can be done by placing two chips face-to-face in a manner that aligns the transmitter circuits of one chip with the receiver circuits of the other. The two chips communicate by capacitive coupling, in which transmitters drive a plate of metal on one chip that couples to a corresponding plate of metal on the other chip.
Coplanarity concern is important in the semiconductor package having chip with the function of proximity communication. Conventionally, a ceramic substrate is usually applied in this semiconductor package. In order to cost down, it is a trend to use an organic substrate in stead of the ceramic substrate in some semiconductor package. However, warpage effect arises in the semiconductor package having the organic substrate. Therefore, how to reduce the warpage effect on the organic substrate for coplanarity concern is an important issue to be resolved.